An important performance feature in laundry detergents is the ability to remove clay-type soils from fabrics and to keep soils in suspension so they do not deposit on fabrics during the washing process. The prior an reveals numerous materials (usually referred to as antideposition agents or co-builders) which have been used for this purpose. For example, U.S. Pat. No. 4,407,722, Davies et al., issued Oct. 4, 1983 discloses, inter alia salts of homo- or copolymers of acrylic acid or substituted acrylic acid, ethylene maleic anhydride copolymers, polyitaconic acid, certain phosphate esters, diphosphonate salts such as ethane-1-hydroxy-1,1 diphosphonate and salts of polyaspartic acid as antideposition agents.
U.S. Pat. No. 4,490,217, Spadini et al., issued Dec. 25, 1984 discloses the use of mixtures of polyethylene glycol and polyacrylate polymer to achieve a high level of clay-soil removal and anti-deposition performance in detergent compositions built with non-phosphorous builders such as zeolites, sodium carbonate and polycarboxylic acids (e.g., nitrilotriacetic acid, oxydisuccinic acid, etc.).
Polyamino acids and their salts are particularly desirable clay soil removal/antideposition agents for use in detergents because they are highly biodegradable (see European Application EP 454,126, published Oct. 30, 1991). While providing excellent performance in granular detergents, their performance in liquid laundry detergents is somewhat deficient. This is believed to be mainly due to the typically lower pH (usually about 7 to 8.5) of the liquid products.
The object of the present invention is to improve the clay soil removal/anti-deposition performance of polyamino acids (and their salts) in liquid laundry detergents.
All percentages and proportions herein are "by weight" unless specified otherwise.